1. Field of Invention
The present invention relates to a control integrated circuit (IC), especially to a control IC for color sequential liquid crystal displays.
2. Description of Related Art
Nowadays due to advanced technology, various new information products are developed and promoted to meet people's requirements. The conventional display device has shortages of large volume, high power consumption and high radiation dose while the liquid crystal display (LCD) features on compact volume, light weight, low radiation dose and low power consumption. Thus the conventional display device is replaced with the LCD which has become a main stream of a current display market. However, the conventional LCD uses color filters for converting light beams into three color light beams-red, green and blue since there are three primary colors required for each pixel. To create a color image, there are three subpixels in each pixel-red, green and blue, respectively corresponding to red, green and blue color filters. Due to persistence of vision, the human eye receives red, green and blue light through the color filters and perceives pixel color. The light transmission of the LCD and single pixel (dot) size are limited by the color filter. Thus display quality of the LCD is affected by the color filter.
In order to solve the above mentioned problem, a color sequential LCD has been developed. In the color sequential display, three primary colors of each pixel are displayed sequentially. A frame is decomposed into red, green, and blue fields displayed in successively. The three fields are illuminated by the red, green, and blue backlight accordingly. Relying on the human vision system, the successive images are fused into a color image. Thus the sequential display includes no color filter. Moreover, in contrast to pixel size of the LCD with color filter, the pixel size of the sequential display is smaller. Therefore, the color sequential display has higher resolution with lower cost.
Refer to FIG. 1, a block diagram of control circuit of a conventional color sequential display is disclosed. The control circuit of the conventional color sequential display consists of a light-source driving circuit 10, a data driving circuit 12, a scan driving circuit 14 and a microcontroller 16. The light-source driving circuit 10 generates a plurality of driving signals that are sent to a backlight module 22 of a display panel 20 so as to generate a plurality of color backlights. The data driving circuit 12 and the scan driving circuit 14 respectively generate a data signal and a scan signal that are sent to a display module 24 of the display panel 20. According to the data signal, the scan signal and the plurality of backlight colors, a frame is shown.
The microprocessor 16 generates corresponding time signals according to the frames intended to be displayed and the time signals are sent to the light-source driving circuit 10 and the scan driving circuit 14 for timing control of the generated scan signals and driving signals. And the display data is sent to the data driving circuit 12. Generally, the microprocessor 16 needs to control timing of the scan data from the scan driving circuit 14 matching timing of the drive signal from the light-source driving circuit 10 so as to make timing of the scan signal matches timing of the backlight module generating the color backlights. Yet the microprocessor 16 is not only for control of the color sequential display, it also used for control of electronics disposed with itself such as handhold game consoles, and digital photo frames. This means the microprocessor 16 needs to execute commands and launch applications of the electronics. Due to heavy of the microprocessor 16, the electronics are unable to run smoothly. Moreover, the microprocessor 16 generates clock signals through program operation or calculation of an internal counter so that timing of the light-source driving circuit 10 and timing of the scan driving circuit 14 are unable to be precisely controlled and matched with each other. Thus the scan signals generated by the scan driving circuit 14 are also unable to match the color backlights generated by the backlight module 22 precisely. Therefore, quality of the frame displayed on the display panel 20 is under the influence.
Furthermore, the microprocessor 16 requires additional several pins such as GPIO pins for timing control of the light-source driving circuit 10 and the scan driving circuit 14 so as to make them match each other. Thus the number of pins of the microprocessor 16 is increased and the occupied are also increased so that the cost is raised. The volume of the electronic is highly related to the area of the whole control circuit occupied. Thus the compact volume and light weighted requirements of the device are unable to be achieved. In addition, an external Power IC 18 is used as a high-voltage power supply to provide power to the light-source driving circuit 10, the data driving circuit 12, and the scan driving circuit 14. This also leads to increasing of the cost.
Thus there is a need to provide a control IC for the color sequential LCD that overcomes shortcomings of conventional color sequential LCD such as overloading of the microprocessor and large occupied area and enables the scan driving circuit to match the light-source driving circuit precisely for solving the problems mentioned above.